Stupid question - in DTW, why not reuse the runoff?

[phxazcraig]

Currently in flower in my fist coco grow, which is going well.

I end up with a bucket of runoff every other day or so, which I've been using to feed houseplants and yard plants. (And boy have some of them gone on a growth spurt!)

Currently I'm inputting nutes with EC just under 1500. It's currently running about 1400 EC (or less, typically) in the runoff.

What are the reasons for NOT just basically throwing it back into the reservoir, perhaps after adjusting the EC in some way?

 

[tobh]

imo it's primarily a concern of being able to sterilize the waste solution. @Dirtbag runs a UV-C sterilizer and recirculates his runoff, but he also runs H2o2 (as do I). It can also throw your ratios off since there's no real way to determine everything the plant consumed in a given period.

Even when I was running recirculating with hydroton, I changed my reservoir weekly just to ensure the ratios stayed relatively close to what they started as.

It's doable and a lot of people have done it successfully, but you'll need to ensure you're keeping EC in check. You'll also need to stay on top of ensuring pH stays stable, and no pathogens take hold.

 

[phxazcraig]

imo it's primarily a concern of being able to sterilize the waste solution. @Dirtbag runs a UV-C sterilizer and recirculates his runoff, but he also runs H2o2 (as do I). It can also throw your ratios off since there's no real way to determine everything the plant consumed in a given period.

Even when I was running recirculating with hydroton, I changed my reservoir weekly just to ensure the ratios stayed relatively close to what they started as.

It's doable and a lot of people have done it successfully, but you'll need to ensure you're keeping EC in check. You'll also need to stay on top of ensuring pH stays stable, and no pathogens take hold.

Ph is controlled by Bluelab in the reservoir, so that is stable. My EC is typically lower than input, but in the past week or two that is changing and going up. I think it has to do with flowering and reducing the lights to 12/12.

There are times it seems so easy to dump a bucket of decent runoff back into the reservoir than mixing up another 10 gallons.

 

[tobh]

Ph is controlled by Bluelab in the reservoir, so that is stable. My EC is typically lower than input, but in the past week or two that is changing and going up. I think it has to do with flowering and reducing the lights to 12/12.

There are times it seems so easy to dump a bucket of decent runoff back into the reservoir than mixing up another 10 gallons.

not really relevant to the thread topic, but seeing EC rise in runoff is definitely an indicator you need to drop input EC a little bit.

You can definitely do recirculating with DTW, it just requires additional equipment and monitoring to ensure you don't end up with crazy swings in either EC or pH, and of course pathogens are always a concern. I wouldn't rely on a doser to keep pH stable either as too much pH up or down will skew your ratios and eventually you might end up with 200ppm (not a real number, just throwing out a hypothetical) of pH buffer alone -- not a good situation to be in.

Of course you can give it a shot and see how it works for you. The big pushback on it with coco is experienced growers don't want new coco growers getting in over their heads as things can go sideways fast with recirculating DTW in coco. Keeping the barrier to entry lower helps everyone in the long run, and once someone is comfortable with the media they can do whatever they want.